ECMAScript symbol keys are not showing up in TypeLiteral.getType().getProperties()

**Describe the bug**

I'm able to pick up string and number keys of type literals just fine. But if I have a symbol key, it's invisible.

Version: 17.0.1

[ECMAScript symbols](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol) are not a well-known feature of the ECMAScript standard, but they have been around a while.

Test:
```ts
import { Project } from "ts-morph";

const project = new Project();
const sourceFile = project.createSourceFile("test.ts", `
const KeySymbol = Symbol("key");
type OneTwoKeyLiteral = {
one: false;
two: false;
[KeySymbol]: "key";
};
`);

// reproduce the problem here

const alias = sourceFile.getTypeAliasOrThrow("OneTwoKeyLiteral");
console.log(alias.getText()); // [KeySymbol] shows up as a property
console.log(alias.getType().getProperties().map(s => s.getName()); // ["foo", "bar"]
```

**Expected behavior**

The last line should log ` ["foo", "bar", "KeySymbol"].

The funny thing is, [ts-ast-viewer is inconsistent on this](
https://ts-ast-viewer.com/#code/MYewdgzgLgBA0gUwJ4GUkFsBGIA2MC8MaWuAFAEQDWy5AlANwBQUSADgjLIQN4zgIAuGADMAhjggIANJwDuIIVABOAV2kwA2olQZsOALowh5YSBDkYAXybM2HFQRjUkIYZyZA):

1. The TypeLiteral node has three members in the "Node" panel.
2. The TypeLiteral node has two members in the "Symbol" panel.
3. The TypeOfOperator node shows three types in the "Type" panel.